1. Field of the Invention
The present invention relates to a gear train of an automatic transmission for a vehicle including a simple planetary gear set, a compound planetary gear set, three clutches, and two brakes, and thus, the gear train of an automatic transmission of the present invention may realize six forward speeds and one reverse speed.
2. Description of Related Art
A typical shift mechanism of an automatic transmission utilizes a combination of a plurality of planetary gear sets. A gear train of such an automatic transmission that includes the plurality of planetary gear sets changes rotating speed and torque received from a torque converter of the automatic transmission, and accordingly changes and transmits the changed torque to an output shaft.
It is well known that when a transmission realizes a greater number of shift speeds, speed ratios of the transmission can be more optimally designed and therefore a vehicle can have better fuel mileage and better performance. For that reason, an automatic transmission that enables more shift speeds is under constant investigation.
In addition, with the same number of speeds, features of a gear train such as durability, efficiency in power transmission, and size depend a lot on the layout of combined planetary gear sets. Therefore, designs for a combining structure of a gear train are also under constant investigation.
For a manual transmission, too many speeds cause a driver the inconvenience of excessive manual shifting. However, for an automatic transmission, a transmission control unit automatically executes shifting by controlling the operation of the gear train, and therefore more speeds usually implies more merit.
A four speed automatic transmission or a five-speed automatic transmission has been widely used, but nowadays, a six-speed automatic transmission is increasingly used.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.